Edit the phases and it is available for Admins/Owners.
From inside the Project detail page click on the Edit button, in the top right corner.
Select the Phases tab, you'll see a full list of all the phases you have created for the current Project.
Here are the elements you can edit on this page:
the Active checkbox to see what phases are still active;
the Name and Category column;
the Budget (in hours)
Every time you make a change, please remember to Save, otherwise, your changes won't be applied.
If you would like to create a new phase for the current project, just click on Add new and a new line will appear at the top of the table.